In hospitals it is common to have sensors monitoring patients by sensing a variety of parameters. These sensors monitor, among other things, heart rate, breathing rate, and various blood gases, including the oxygen content in the blood. The medical instruments that analyze and display the data from these sensors are typically located some distance from the patient and the sensors. A variety of cables connect these sensors to the instruments and often transmit electrical signals containing the sensor data from the patient to the instruments. Because these sensors are connected to, or used near patients, very low electrical currents and voltages are preferably used in these sensors and cables. As a result, the signals from the sensors are subject to electromagnetic interference ("EMI") from a variety of sources, including room lights, electric wall outlets, and other electrical devices. Radio Frequency interference, or RF interference also presents a concern, but all types of interference will be referred to as EMI for convenience in this application.
One medical device subject to this EMI is a blood oximeter. The sensor cables connect to this oximeter through a cable that connects to an instrument casing containing the electronic analysis equipment. The cable connects to the instrument through a widely used plastic coupling or connector made by Hypertronics, with the connector comprising a plurality of male pins that are inserted into a corresponding socket connected to the oximeter instrument housing. A resilient lever hook holds the two parts together. To reduce EMI disruption of the signals, the sensor cable is shielded. Further, the instrument housing is also shielded, as is the cable inside the instrument. Similar shielding steps are used in the cables on other medical instruments where these cable connectors are used.
But despite the shielding in the instrument casing and cable, sensor signals from this oximeter are subject to interference from even the 60 Hz florescent lights commonly used in hospitals. There is thus a need for improved performance of medical devices in general, and from this oximeter in particular. Further, there is a need for a way to reduce or eliminate EMI disruption and distortion of the signals from these medical instruments in general, and for medical equipment using this particular Hypertronics connector in particular.